1. Field of the Invention
The present invention pertains to a device package wall feedthrough assembly which is metallized. The invention more particularly concerns a fiber optic device package wall feedthrough which is metallized post assembly.
2. Discussion of the Background
Components found inside optical devices such as optical transmitters, detectors, modulators, amplifiers including diodes and exposed, uninsulated conductors, such as wire bonds, may be susceptible to environmental contaminates and/or residual assembly organics such as resins or fluxes which can result in galvanic corrosion and other failure modes which cause the optical device to no longer operate in an acceptable manner. Thus, the interior region of the optical device may be either evacuated or filled with an inert element such as nitrogen. Typically, the device housings are then hermetically sealed. However, a problem exists as to how the optical signal will penetrate the housing whilst maintaining hermeticity and without unacceptable degradation in the transmission properties of the optical signal. A number of general solutions have been developed to solve the problem which typically involve the metallization of an optical fiber over a portion of its length prior to assembly with the feedthrough components which then allow for the formation of a hermetic seal during the assembly process typically through the use of a soft solder alloy. These designs may also take account of the stresses created during assembly process and give due consideration to the reduction of these stresses through design and assembly methodology. Such considerations are of particular interest when employing polarization maintaining fibers. The feedthrough is then subsequently soft soldered into a feedthrough tube that has previously been sealed typically by brazing, into an aperture extending through the device package wall.
Manufacturing such a device is expensive due to the multiple metallizing steps and assembly steps which are followed by soldering steps. Further the current feedthrough designs typically only take account of a single optical fiber within the assembly. There is a growing need to be able to provide multifiber feedthrough designs. With current design approaches and assembly methodologies these are likely to be expensive and difficult to produce.
Therefore, there is a need for a hermetic seal between an optical fiber or fibers and the package wall of a device which provides design flexibility, is easy to manufacture, is cost effective and which does not significantly degrade the transmission properties of the optical signal or signals that the optical fiber or fibers contain.
Therefore, it is an object of the present invention to provide a process and assembly methodolgy which can provide for a hermetic seal between an optical fiber and a package wall.
It is still another object of the invention to provide a metallized fiber optic cable which requires a minimal number of parts and processes.
Yet another object of the invention is to provide a metallized fiber optic cable which is metallized after it is assembled to a sleeve.
It is a further object of the invention to provide a metallized fiber optic cable which is easy to install.
Another object of the invention is to provide a metallized fiber optic cable which is inexpensive to manufacture.
In one form of the invention, the assembly includes a first element having a first surface and a second element having a second surface. The first element positioned adjacent to and contacting the second element so as to form a gap between the first element and the second element. A layer of a metallic material is then adhered to a portion of the first surface of the first element and to a portion of the second surface of the second element so as to form a hermetic seal between the first element and the second element at the gap.
In another form of the invention, the assembly includes a first element having a first surface and a second element having a second surface. The first surface includes first, second, and third portions. The second surface includes fourth, fifth, and sixth portions. The second surface of the second element facing the first surface of the first element, and the first portion of the first surface contacts the fourth portion of the second surface so as to form a gap between the first element and the second element. A layer of a metallic material is then adhered to the third portion of the first surface of the first element and to the sixth portion of the second surface of the second element so as to form a hermetic seal at the gap.
In still another form of the invention, the assembly includes a fiber optic cable and a ferrule. The fiber optic cable includes an optical fiber substantially surrounded by a sheath. The optical fiber is made of an optically transparent material. The sheath is made of a polymer material. The ferrule includes a large opening and a small opening. The ferrule is made of a ceramic material. When the fiber optic cable is mounted to the ferrule, the optical fiber is positioned within the small opening and the sheath is positioned in the large opening. A gap is formed between the optical fiber and the small opening. A layer of a metallic material is adhered to a portion of the optical fiber and the ferrule so as to form a hermetic seal at the gap.
In still yet another form of the invention, the assembly includes a process for metallizing two elements to each other. The process includes the first step of placing a first element adjacent to the second element so as to form a device. The device includes a gap between the first element and the second element. Following the first step is the second step. The second step includes the step of adhering a layer of a metallic material on the device so as to form a hermetic seal at the gap.
Thus, the invention is superior to existing devices or processes for passing a fiber optic cable through a wall of a detector and to hermetically seal it thereto. The invention reduces the number of parts and processes required to provide the hermetic seal. Furthermore, the invention provides a device which is inexpensive to produce, while at the same time being easy to manufacture, install, and use. These and other features of the invention are set forth below in the following detailed description of the presently preferred embodiments.